1. Field of the Invention
The present invention relates to a data storage device having a storage medium such as a memory for storing data including confidential data, more particularly to a data storage device which prevents stored data from being irregularly read out, and a detection method for detecting dismantlement of a storage device housing.
2. Description of the Related Art
Conventional computer systems for processing charge affairs by dealing with monetary data have usually employed key cryptography system in order to encrypt (encode) monetary data when updating the data. In such the computer system, a data storage device stores confidential data such as keys for cryptography in order to prevent the monetary data from being falsified.
In order to prevent stored data from being irregularly read out (stolen) by an unqualified person, data storage device generally performs predetermined processing when it detects dismantlement of the device (housing). For example, a conventional storage device has employed micro switches arranged in its cover or the like, in order to detect dismantlement of the device by sensing signal changes caused by the micro switches.
Such the conventional storage device comprising the micro switches, however, could not find dismantlement perfectly, because the micro switches are not switched if portions having no switches are processed to dismantle the device. In other words, once position of the micro switches is revealed, the conventional storage device is no longer effective in data protection.